1. Field of the Invention
This invention relates to lighting and more particularly to traffic signal lamps.
2. Description of the Prior Art
It is well known that when a lens of a lamp has dirt particles deposited thereon, the dirt increases the opacity of the lens. The increase of the opacity causes a decrease of intensity of transmitted light from the lamp thereby making the light from the lamp difficult to see. Accordingly, the increase of the opacity is undesirable.
Usually, a traffic signal lamp assembly is mounted above the ground at a level which is not easily reached. Therefore, when lenses of the lamp assembly have the increased opacity due to dirt, the lenses are not cleaned. It should be appreciated that when the increased opacity decreases the intensity of light from the lamp assembly, motorists and pedestrians are endangered.
Accordingly, there is a need for a traffic signal lamp assembly having lenses which are cleaned automatically.